1. Field of the Invention
The present invention generally relates to a refrigerant compressor and, more specifically, to an improvement in a discharge valve and a retainer element assembly by which the physical durability of a discharge valve element of the refrigerant compressor may be surely improved.
2. Description of the Related Art
Many refrigerant compressors are known and one typical conventional compressor is a double-headed piston type swash-plate-operated refrigerant compressor as shown in FIG. 3.
Referring to FIG. 3, the conventional refrigerant compressor includes a front cylinder block 80 and a rear cylinder block 81 which are disposed in an end-to-end relation to form a combined cylinder block. A plurality of cylinder bores 80a and 81a for forming compression chambers are formed in the front cylinder block 80 and the rear cylinder block 81, respectively. Each pair of the cylinder bores 80a and 81a (a pair being one from each set of cylinder bores 80a and 81a) is coaxially aligned. A swash plate chamber 82 is formed in a middle part of the combined cylinder block. A front suction valve element 83 having a plurality of suction valves, a front valve plate 85, a front discharge valve element 87 having a plurality of suction valve portions and, a front retainer element 89 are placed on the front end of the front cylinder block 80. A rear suction valve element 84 having a plurality of suction valve portions, a rear valve plate 86, a discharge valve element 88 having a plurality of discharge valve portions and a rear retainer element 90 are placed on the rear end of the rear cylinder block 81. A front housing 91 and a rear housing 92 are joined to the front end of the front cylinder block 80 and the rear end of the rear cylinder block 81, respectively, and these four elements are combined together with a plurality of through screw bolts 93 to form a housing assembly of the compressor. O-rings are arranged between the front cylinder block 80 and the rear cylinder block 81, between the front cylinder block 80 and the front housing 91, and between the rear cylinder block 81 and the rear housing 92, respectively to hermetically seal the interior of the compressor against the external atmosphere. A drive shaft 94 is supported for rotation in the front housing 91, the front cylinder block 80 and the rear cylinder block 81 via bearings housed in the front and rear cylinder blocks 80 and 81. A swash plate 95 is mounted on the drive shaft 94 for rotation in the swash plate chamber 82 and is fixedly held in place on the drive shaft 94 by thrust bearings. A plurality of double-headed pistons 96 fitted in the cylinder bores 80a and 81a are linked to the swash plate 95 by shoes in contact with the front and the rear surface of the swash plate 95, respectively.
The rear housing 92 has a suction chamber 92a capable of communicating with an external evaporator (not shown) via the swash plate chamber 82, and a discharge chamber 92b capable of communicating with an external condenser (not shown). The suction chamber 92a and the discharge chamber 92b are defined by partition walls 92c and 92d. The rear valve plate 86 is provided with suction ports 86a connecting the suction chamber 92a and the cylinder bores 81a via the suction valves of the rear suction valve element 84, and discharge ports 86b connecting the discharge chamber 92b and the cylinder bores 81a via the discharge valve portions of the rear discharge valve element 88. The rear suction valve element 84 has a base portion held between the rear cylinder block 81 and the rear valve plate 86, and the suction valve portions extending from the base portion and capable of being elastically moved to open the suction ports 86a into the suction chamber 92a.
As shown in FIG. 4, the rear discharge valve element 88 has a base portion 88a held between the valve plate 86 and the rear housing 92, and the valve portions 88b extending from the base portion 88a and capable of being elastically moved to open the discharge ports 86b into the discharge chamber 92b. The retainer element 90 has a base end portion 90a in contact with the base portion 88a of the rear valve element 88 and controlling portions 90b extend from the base end 90a to control the opening of the respective valve portions 88b of the rear valve element 88. The respective controlling portions 90b are arranged to be in registration with the respective valve portions 88b of the rear valve element 88 and are curved into the interior of the discharge chamber 92b. The front and the rear surface of the retainer element 90 are coated with elastic layers (not shown) e.g., rubber layers or the like, so that the retainer element 90 may exhibit the function of gasket.
It should be noted that the front suction valve element 83, the front valve plate 85, the front discharge valve element 87, the front retainer element 89 and, the front housing 91 on the front end of the front cylinder block 80 are basically constructed using the same design principle as that of the above-described respective elements, i.e., the rear suction valve element 84, the rear valve plate 86, the rear discharge valve element 88, the rear retainer element 90 and the rear housing 92.
When the drive shaft 94 of the compressor is driven to rotate, the swash plate 95 drives the double headed pistons 96 to reciprocate in the cylinder bores 80a and 81a. Consequently, for example, on the rear side, a low-pressure refrigerant gas is sucked into the cylinder bores 81a from the suction chambers 92a, via the suction ports 86a and the valve portions of the rear suction valve element 84, and the refrigerant gas is compressed and discharged from the cylinder bores 81a into the discharge chamber 92b via the discharge port 86b, and the valve portions 88b of the rear discharge valve 88. The refrigerant gas is sucked into and discharged from the cylinder bores 80a on the front side in the same way.
In the compressor incorporating the foregoing front and rear discharge valve elements and front and rear retainer elements therein, it has been recently found that the valve portions of the respective discharge valve elements are unsatisfactory in physical or mechanical durability. Namely, as shown in FIG. 4, in the conventional typical refrigerant compressor, for example, the partition wall 92c of the rear housing 92 has a holding portion 92d arranged to come into contact with the base portion 90a of the retainer element 90 when assembled, and a relieved portion 92e formed as a large cut recessed from a plane including the holding portion 92d in the extending direction of the valve parts 88b. In the compressor, the base end portion 90a of the rear retainer element 90 is pressed by the holding portion 92d of the rear housing 92 due to a clamping force exhibited by the through screw bolts 93 (FIG. 2) to fixedly hold the base portions 88a of the rear discharge valve element 88 and the base end portions 90a of the retainer element 90 between the valve plate 86 and the rear housing 92.
In the described compressor, each relieved portion 92e is formed as a large cut recessed from a plane containing the holding portion 92d, and an edge 92f of the relieved portion 92e on the side of the valve portion 88b is spaced far from the back surface of the corresponding controlling portion 90b of the retainer element 90. Therefore, a large amount of deformation of each controlling portion 90b of the retainer element 90 easily occurs in the discharge chamber 92b, to take the shape indicated by the alternate long and two short dashes lines. The deformation of the controlling portion 90b of the retainer element 90 is specifically generated when the compressor operates in a liquid compression mode. Accordingly, there is a possibility that the valve portions 88b of the rear discharge valve element 88 are irregularly moved and twisted in the controlling portions 90b of the retainer element 90 to cause fatigue of the rear discharge element 90 and thus shortening the life of the rear discharge valve element 90.
Such a problem may be solved by an improvement in which the holding part 92d of the partition wall 92c of the rear housing 92 is formed to be in contact with the base end portion 90a of the retainer element 90, and a relieved portion 92g is formed to extend from the holding part 92d in a direction in which the valve portions 88b extends, while gradually receding to form a curved wall as shown in FIG. 5. In this connection, Japanese Unexamined Utility Model Publication (Kokai) No. 51-1436410 (JU-A-51-1436410) and U.S. Pat. No. 5,100,306 (U.S. Pat. No. 5,100,306) disclose compressors which include a discharge valve and retainer element assembly having a structure similar to the above-mentioned improvement in association with the discharge valves 88. Namely, as is understood from the illustration of FIG. 5, in the known compressors of JU-A-51-143641, and U.S. Pat. No. 5,100,306, the edge 92h of the relieved portion 92g arranged to be in registration with a portion of the valve portion 88b is not spaced far from the back surface of each control portion 90b of the retainer element 90, and hence the deformation of the control portion 90b of the retainer element 90 in the discharge chamber 92b during controlling of the opening of the discharge valve element 88 can be prevented.
Therefore, in the above-mentioned compressors, it is considered that the deterioration in the physical durability of all valve portions 88b of the discharge valve element 88 due to the deformation of the controlling portions 90b of the retainer element 90, that may occur during an opening control operation, can be prevented.
Nevertheless, the elastic layers of the retainer element 90 are easily compressed when the base end portions 90a of the retainer element 90 are pressed by the fastening force of through screw bolts (FIG. 3) or the like exerted thereon through the holding portions 92d of the rear housing 92 when assembling the compressor. Thus, the compressed elastic layers bulge out onto the relieved portions 92g. Since each relieved portion 92g of the partition wall 92c extends from the corresponding holding portion 92d in the extending direction of the valve portion 88b and recedes gradually in a curve, the relieved portion 92b is liable to press the control portion 90b of the retainer element 90. Therefore, a bending position (fulcrum) of each valve portion 88b of the discharge valve element 88 at which each valve portion 88b bends to perform an opening and a closing motion thereof must be shifted in the direction of extension of the valve portion 88b from a true fulcrum position. This shifting of the fulcrum of each valve portion 88b of the discharge valve element 88 is caused by not only a deterioration of the elastic layers of the retainer element 90 after a long period of use but also a possible damage to the elastic layers of the retainer element 90 during assembling the compressor. If each controlling portion 90b of the retainer element 90 is thus distorted, the elastic modulus of the valve portion 88b of the discharge valve element 88 increases to make it difficult to open the discharge port 86b, and an excessive bending stress is induced in all valve portions 88b of the discharge valve element 88 to reduce the operation life of the valve portions 88b by fatigue.
Further, JU-A-6-40389 and European Patent Publication No. 0595313B1 disclose a different discharge valve element and a retainer element assembly of a refrigerant compressor, in which a partition wall of a rear housing defining a discharge chamber is provided with a holding portion similar to the afore-mentioned holding portion of the rear housing 92, and the discharge chamber is used as a relieved portion for a retainer element. The retainer element is supported, at its back surface portions extending along valve portions of a discharge valve element, by a support wall of the rear housing in the shape of a projection portion projecting from a housing wall into the discharge chamber. Since the discharge chamber of the compressor serving as the relieved portion for the retainer element is recessed far from a plane in which the holding portion of the rear housing lies, the relieved portion does not include any portion exerting a pressure on the elastic layers of the retainer element when the base end portions of the retainer element are pressed by the above-mentioned holding portion. Thus, the controlling portions of the retainer element can be prevented from being deformed. Accordingly, a change in the elastic modulus of the valve portions of the discharge valve element and a deterioration in the physical durability of the valve portions of the discharge valve element can be surely prevented.
Further, in the above-described compressor, since the back surface of the retainer element is supported by the support wall (the projection portion) of the rear housing when the controlling portions of the retainer element control the opening of the valve portions, any deterioration in the physical durability of the valve portions of the discharge valve element due to the deformation of the controlling portions of the retainer element can be prevented.
Nevertheless, since the support wall or the projection portion of the rear housing of the above-described refrigerant compressor is formed separately from a partition wall defining the discharge chamber, an additional process to produce the support wall for supporting the controlling portions of the retainer element is required in addition to a process to produce the holding portion on the partition wall of the rear housing defining the discharge chamber. Thus, an increase in the production process of the rear housing eventually increases the manufacturing cost of the refrigerant compressor. Moreover, the support wall of the rear housing projecting into the discharge chamber may provide an obstruction to a flow of the refrigerant gas in the discharge chamber. Further, since the support wall of the rear housing necessarily causes a reduction in a volume of the discharge chamber, there is a possibility of causing a pulsation in a pressure of the compressed refrigerant gas when the compressed refrigerant gas is delivered from the discharge chamber toward an external refrigerating circuit.
The describe problems are encountered by all types of refrigerant compressors employing the above-described discharge valve element and retainer element assembly in addition to the double-headed piston type swash-plate-operated refrigerant compressor.